DIELECTRIC LOSS AND RELAXATION TIME IN ROSIN

Abstract

The power factor, dielectric loss and capacitance at 60 cycles of abietic acid have been measured over the temperature range 20° to 100°C. Short time charge and discharge curves, beginning 0.001 sec. after the application or removal of voltage, taken with the amplifier oscillograph, have permitted direct measurement of the relaxation time over the same temperature range. It is shown in general that there are two principal components of the discharge curve which lead to two types of relaxation time, one being the principal factor in the dielectric loss at low temperatures, and the other at high temperatures. The discharge curves have been used for an analysis of the alternating current behavior following the method of von Schweidler. There is uniform agreement between measured and computed loss. With increasing temperature the dielectric constant rises from about 2.6 to 2.8 within the temperature interval 20° to 50°C, the maximum rate of rise being at about 30°, at which temperature the maximum of power factor is also observed. The results are discussed in the light of dielectric absorption in the Maxwell sense and of Debye's theory of polar molecules. The conclusion is reached that alternating current measurements at 60 cycles do not offer a promising method of distinguishing between the two theories, since the same behavior is predicted by each.